The present invention relates generally to the synthesis of ansa-metallocene compounds. These ansa-metallocene compounds may be used as components in a multi-component catalyst system, ultimately for use in olefin polymerizations or other catalytic processes. More specifically, this invention relates to methods for the stereoselective synthesis of certain bridged metallocene compounds.
Often, an isomer of a particular ansa-metallocene compound, such as the rac isomer instead of the meso isomer, may provide performance advantages such as improved control of tacticity, e.g., for producing isotactic polypropylene. However, isolating and purifying a desired isomer from a rac/meso isomer mixture may be very difficult, and is not always possible.
It would be beneficial to develop new synthetic methods to produce stereo-enriched ansa-metallocenes in an acceptable isomer selectivity such that additional isolation or purification steps are neither necessary nor required. Accordingly, it is to this end that the present invention is directed.